At present, moderate- or low-temperature sealing reagents are widely used to reduce the porosity and adsorption capacity of anodic oxide films in the processing after aluminum alloy anodizing. Such reagents are convenient to use, and many of them contain nickel ions. Because of nickel allergy caused by frequent contact of nickel containing metal ornamentals with human body, there are standards in many countries that limit the use of nickel-containing ornamentals, such as BS EN 1811:1999 and BS EN 12472:2005. Therefore, nickel-free sealing reagents for aluminum alloy anodizing are urgently needed.
In prior art, a relatively mature nickel-free sealing reagent is fluotitanate moderate temperature sealing reagents. For example, a sealing reagent includes 5-10 g/L potassium fluotitanate, 0.05-0.15 g/L cyclohexanone and 0.05-0.15 g/L isoamyl alcohol. It is used at the temperature of 55-65° C., and the treatment time is 1.0-1.5 μm/min. This sealing reagent is nickel-free, but some dyed workpieces lose weight significantly after processing by this sealing reagent.